In general, in a hydraulic excavator as a typical example of the construction machine, a gate lock lever which can switch between a lock position where driving of a hydraulic actuator (a hydraulic cylinder of a working mechanism, a traveling hydraulic motor of a lower traveling structure, and a revolving hydraulic motor of an upper revolving structure, for example) is prohibited and an unlock position where the driving of the hydraulic actuator is allowed is disposed on an entranceway side to an operator's seat (Patent Document 1). The gate lock lever is operated by an operator to a raised position which is a lock position and to a lowered position which is an unlock position.
When an operator gets on the operator's seat of the hydraulic excavator or gets off the operator's seat, for example, the gate lock lever is operated to be raised to the lock position (raised position). On the other hand, when the operator operates the hydraulic excavator on the operator's seat, the gate lock lever is operated to be lowered to the unlock position (lowered position). Here, a gate lock switch is provided in the gate lock lever.
When the gate lock lever is operated to the lock position, the gate lock switch is turned OFF, and a valve device for switching supply/discharge of a pressurized oil to a pilot operation system is switched to a shut-off position (discharge position). In this case, stop of the hydraulic actuator is maintained, and an operation of the working mechanism, a revolving operation of the upper revolving structure, and a traveling operation of the lower traveling structure are disabled. On the other hand, when the gate lock lever is operated to the unlock position, the gate lock switch is turned ON, and the valve device is switched to a supply position. In this case, the hydraulic actuator is driven in accordance with the operation by the operator, and the operation of the working mechanism, the revolving operation of the upper revolving structure, and the traveling operation of the lower traveling structure are enabled.